Pest of the Month - October 2009

by: Aparna Gazula, Commercial Horticulture Agent

A New Exotic Soft Scale Insect on Croton

INTRODUCTION: Division of Plant Industry inspector Lynn Howerton collected this new-to-science record on April 9, 2008 at a nursery in Marathon (Monroe County), Florida. The host plant was croton (Codiaeum variegatum (L.) Blume). Specimens submitted to the Division of Plant Industry were determined to be an unknown, but exotic soft scale insect (Hemiptera: Coccidae). Subsequent collections of this exotic soft scale on croton have been made from Broward, Miami-Dade and Palm Beach counties.

Identification: Field specimens appear very similar to individuals of the genus Philephedra, but differ in that this species does not produce an ovisac. Specimens were sent to various specialists and there was a preliminary identification of this scale as being Philephedra sp. nr. crescentiae (Cockerell). However, there was some disagreement over the placement of this exotic scale into the genus Philephedra and specimens were shared with Dr. Chris Hodgson (National Museum of Wales, England) for confirmation/determination. Dr. Hodgson indicated that this new exotic scale insect did not fit into Philephedra and is most likely an undescribed species in an undescribed genus of unknown origin. Currently, efforts are being made to describe this new scale insect.

DESCRIPTION: Adult females and late instars of this new exotic soft scale (Fig. 1) have a greenish yellow appearance with dark striations and are approximately 3.5 mm to 7.0 mm long by 2.0 mm wide. Immature male covers are smaller than the female scales and have a glassy appearance. Adult males are small orange bodied gnat-like insects with white wax tail filaments (Fig. 2). This scale superficially resembles a common South Florida scale, Philephedra tuberculosa Nakahara & Gill (Fig. 3), but does not produce an ovisac. Other scales that might be confused with this new exotic scale are young females of Pulvinaria psidii (green shield scale) (Fig. 4) and Pulvinaria urbicola (urbicola scale) (Fig. 5) before they produce ovisacs.

HOSTS: Croton (Codiaeum variegatum (L.) Blume), guava (Psidium guajava L.), mysore fig (Ficus mysorensis Roth), strangler fig (Ficus aurea Nutt.), mango (Mangifera indica L.), Ardisia escallonoides Schiede & Deppe ex Schltdl. & Cham. (Island marlberry), Cupania glabra Sw. (Florida toadwood), Hamelia patens Jacq. (Scarletbush), Psychotria nervosa Sw. (Wild Coffee) and Zanthoxylum flavum Vahl (West Indian satinwood).
ECONOMIC IMPORTANCE: The economic importance of this new soft scale is unknown at this time. It appears that this scale does build up high density populations on croton and may be a pest for this host.
CONTROLS: For controls, please see the University of Florida pesticide recommendations for scale insects on woody ornamentals (http://edis.ifas.ufl.edu/mg005) or contact your local county extension office (http://solutionsforyourlife.ufl.edu/map/index.html)
NATURAL ENEMIES: No natural enemies have been found in samples submitted to the Division of Plant Industry.

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